I have a vanguard in 257 wby mag. It's made by Howa. It shoots great, sub-moa with my handloads very consistently.
The trigger on mine was a sorry piece of crap. Life's too short to shoot a crappy trigger. I put on a Timney trigger. It now shoots like it should, what a difference a trigger makes. Try yours first, you may have a "good" trigger. If not, swap it for a Timney.
I've never looked through a Nikko scope, so I can't comment on it.